If you want to create custom fields to be used across many different forms, you can create global custom fields. These differ from form specific custom fields, in that they can be attached to any form. To create a global custom field, navigate to
Company Data->Advertising->SIM Custom Fields
and click on the add icon in the module title bar, or edit custom field icon.
This will open the Add/Edit Custom field window with the information described in the
Add/Edit Custom Field
section but the global checkbox will not be visible. Every custom field created from this screen will be created as a global custom field.
You can also modify an existing form specific custom field to be global by opening up the form, editing the custom field and checking the global checkbox then saving. Once you save the form the custom field will no longer appear in the form custom field tree view, it will appear in the global custom field lister page.
SIM - Global Custom Fields